The present invention relates to an improved steering axle, and specifically to a steering axle having improved structure for a boss to retain a steering knuckle kingpin.
Forged beam axles are used on a variety of vehicles, including large vehicles such as light trucks and commercial trucks. These axles endure high loads which are transmitted to the axle through the wheel. On a steering axle, a steering knuckle supports the wheel and connects the wheel to the axle. The steering knuckle is attached to the axle with a kingpin. The kingpin is received in a boss on the end of the axle and is kept stationary relative to the axle while the steering knuckle rotates about the kingpin in response to action of the steering linkage. To reduce the likelihood that the kingpin will move relative to the axle, a draw-key is inserted into the assembly. The draw key is inserted through an aperture in the axle boss. The aperture intersects the bore, and the draw key is inserted through the aperture and is positioned between a recess in the kingpin and the boss, thereby preventing movement between the kingpin and the axle. Typically a draw key will have a hex head and a cylindrical shaft with a threaded end. A nut is torqued on the threaded end to secure the draw-key in place.
Loads applied during driving cause some bending action in the axle in the horizontal plane, and at times greater bending forces in the vertical plane. When loads are applied during braking, bending forces in the horizontal plane increase. Depending on the configuration of the axle, the forces on the axle may act as torsional forces causing some twisting action in the axle. On a steering axle, these forces are transmitted to the axle through the kingpin interface with the axle boss, and can adversely affect wear between the kingpin and the axle boss. These forces can also adversely affect the wear of the draw-key and its effectiveness in preventing relative movement between the kingpin and boss. Hence there exists a need for an improved interface between a steering knuckle kingpin and axle.
The present invention provides an improved steering axle providing an improved interface between the steering knuckle kingpin and the axle. The result is an axle better suited to handle the loads applied to the axle through the steering knuckle kingpin and a steering axle boss. The axle includes distal ends, each formed into a boss with a central bore configured to receive the kingpin of a knuckle assembly. The boss additionally includes first and second axially extending and angularly spaced ribs each defining an axial portion having increased thickness. Each rib extends angularly from a location outboard of the bore axis to a location inboard of the bore axis. The boss provides increased rigidity in the area surrounding the kingpin, thereby improving retention of the kingpin and preventing motion between the kingpin and the boss. The boss also improves the fatigue life of the distal end of the axle. The improved steering axle provided herein, provides improved performance without significant increase in weight or cost.
Other aspects of the present invention are provided with reference to the figures and detailed description of embodiments provided herein.